The High Speed Packet Access (HSPA) proposed to support a higher-rate data service, a shorter delay, a higher throughput and spectrum utilization ratio and better coverage of services at a high data rate includes the High Speed Downlink Packet Access (HSDPA) and the High Speed Uplink Packet Access (HSUPA). Particularly, the HSDPA relates to an enhanced and evolved radio part in the standard of Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) to significantly improve a transmission rate of downlink data. A High-Speed Shared Information Channel (HS-SICH) is added in Time Division Duplexing (TDD) HSDPA as an uplink control physical channel responsible for bearing Acknowledgement/Negative Acknowledgement (ACK/NACK) information to a Hybrid-Automatic Repeat reQuest (HARQ) for data over a High Speed Downlink Shared Channel (HS-DSCH) and Channel Quality Indicator (CQI) information and also carrying Transmission Power Control (TPC) and Synchronization Shift (SS) information. However, there is no Transport Format Combination Indicator (TFCI) carried in the HS-SICH. An HS-SICH channel occupies one channelization code with an uplink Spread Factor (SF) of 16, and the timeslot of #5 is usually occupied. The HS-SICH is a shared physical channel so that the same spread code is used for multiple users who are distinguished from one another by an orthogonal sequence. Signaling over the HS-SICH is as shown in Table 1 below.
TABLE 1HARQ ACK/NACK1 bit1-ACK and 0-NACKinformationRTBS6 bitsUE Recommended Transport Block SizeRMF1 bitUE Recommended ModulationFormat: 0-QPSK and 1-16QAMSSDownlink synchroni-zation control wordTPCDownlink power control word
For downlink data to be transmitted, a Node B firstly transmits downlink scheduling and control information over an HS-SCCH to indicate to a UE the presence of HSDPA data over a subsequent High-Speed Physical Downlink Shared Channel (HS-PDSCH), and the UE retrieves a transport block by unscrambling the HS-SCCH and then feeds ACK/NACK information and channel quality indicator information, i.e., a Recommended Transport Block Size (RTBS) and a Recommended Modulation Format (RMF), to the Node B over a corresponding HS-SICH.
The HSPA+ is an evolved version of the HSPA with enhanced uplink and downlink capabilities. The Multiple Input Multiple Output (MIMO) is introduced in the HSPA+ to further improve a data transmission rate and a capacity of the system. In view of issues of implementing a UE in hardware, a consumption cost thereof, etc., downlink transmission of dual streams at most is supported in the MIMO solution in the HSPA+.
For MIMO transmission of dual streams in the TDD HSPA+ system, a branch of high speed data stream is divided into two parallel branches of data streams at a lower rate, which are in turn encoded, interleaved, modulated, etc. Since different encoding rates and symbol mapping schemes may be used for the two branches of data streams, the number of information bits assigned over the respective streams may also vary. Each of the data streams is further divided into a number C of sub-streams (C is the largest number of HS-PDSCHs defined according to the capability of a UE), each of which is further spread and scrambled and then transmitted over multiple antennas.
In order to support MIMO transmission of dual streams, it is necessary to, feed back the acknowledgement of the UE for the data of the dual streams and to recommend to the Node B the number of data streams in the next Transmission Time Interval (TTI) and transport block sizes and modulation formats over the respective data streams, over the HS-SICH. Apparently, this can not be performed over the existing HSDPA HS-SICH.